Many types of hand tools such as knives and multitools incorporate folding mechanisms that allow an implement to be moved between a folded position in which the implement is safely stowed in the tool handle, and an extended position in which the implement is ready for work. One typical example of such a folding tool is a knife having a folding blade. The knife handle typically has two opposed handle portions defining a blade-receiving groove. A blade pivots on a shaft attached to the handle such that in a folded position the blade is stowed with the cutting portion of the blade safely in the groove, and such that in an extended position the blade is extended away from the handle, ready for use. Foldable knives are ubiquitous.
To increase the safety of folding tools such as knives, many such tools incorporate locking mechanisms of one type or another. When the knife blade pivots into the open position, it's pivotal movement is stopped with a transverse blade stop pin housed in the handle. Often a locking mechanism is included that prevents the blade from pivoting back from the open into the closed position. There are many types of locking mechanisms. One common type is a “liner lock.” This kind of mechanism relies upon a resilient lever formed as part of a handle liner. When the blade is pivoted to the open or extended position, the resilient lever engages a cooperatively formed ramp on the blade and thereby locks the blade in the open position. Another typical locking mechanism is a cross-bolt mechanism such as that described in U.S. Pat. No. 5,822,866. As detailed in the '866 patent, which describes an automatic opening knife, the cross-bolt mechanism includes a locking body that has a cylindrically tapered side wall portion. When the blade is extended to the open position, the tapered side wall portion of the locking body is urged by a compression spring into a locking position in which the locking body wedges between an engagement surface on the blade and a bore in the handle to lock the blade in the open position. Both types of knives just described—the liner locking type and the cross-bolt type—and many other knives, rely on a blade stop pin to stop blade rotation in the opening direction. The stop pin is a cylindrical rod that typically abuts a shoulder formed on the blade at the same time the lock mechanism engages.
Most folding knives, including those that use liner locks and those described in the '866 patent are manufactured according to strict manufacturing tolerances. Often these tolerances mandate that there are cumulatively only a few thousandths of an inch tolerance in the assembled product. This means that when manufacturing the numerous parts for a knife, each part has to be within even smaller tolerances for the finished product to meet cumulative specifications. Unfortunately, manufacturing tolerances are not always easily controlled. In a folding knife, out of tolerance or near tolerance parts can add up in the finished product and result in an assembled product that does not meet final quality specifications and does not operate properly.
In the example of a folding knife that uses a stop pin and a locking mechanism, if the assembled product is out of specification, the locking mechanism may not engage properly. To remedy this situation, the unit must be repaired to adjust the locking mechanism so it works properly and to bring it within acceptable specifications. With liner lock knives and cross-bolt knives that use stop pins, this requires that the knife is disassembled and one or more parts replaced or repaired by milling to bring the part or the assembled product within acceptable specification ranges. For example, with a liner lock the liner lever may need to be milled, or the ramp portion of the blade may be milled, or the liner may need to be replaced. With a cross-bolt type of lock, the tapered portion of the locking body and/or the handle may need to be milled. In both cases, the stop pin may also be milled. But regardless of the process that is used to adjust the blade locking mechanism, disassembly, milling and repair and reassembly are time consuming and expensive.
There is a need therefore for an apparatus that allows adjustment of the implement stop position in a folding tool that incorporates an implement stop pin.
The present invention relates to a hand tool handle that incorporates a mechanism for variably adjustment of the stop position of the implement when it is in the open position.